Abstract:

A method and apparatus for tracking resources in a communication network.
A central resource tracking function receives a request to track a
resource from a location application node. The central resource tracking
function broadcasts a subscription message to a plurality of Wireless
Sensor Network Gateway nodes. The subscription message includes an
identifier associated with the tracked resource. The central resource
tracking function then receives a subscription response message from a
first Wireless Sensor Network Gateway node informing the central resource
tracking function that the resource associated with the identifier is
located in the Wireless Sensor Network served by the first Wireless
Sensor Network Gateway node, and receiving from a second Wireless Sensor
Network Gateway node a subscription rejection message.

Claims:

1. A method of tracking resources in a communication network, the method
comprising:at a central resource tracking function, receiving a request
from a location application node to track a resource;broadcasting a
subscription message to a plurality of Wireless Sensor Network Gateway
nodes, the subscription message including an identifier associated with
the tracked resource;receiving from a first Wireless Sensor Network
Gateway node a subscription response message informing the central
resource tracking function that the resource associated with the
identifier is located in the Wireless Sensor Network served by the first
Wireless Sensor Network Gateway node; andreceiving from a second Wireless
Sensor Network Gateway node a subscription rejection message.

2. The method according to claim 1, further comprising:at the second
Wireless Sensor Network Gateway node, storing a record of the
subscription message.

3. The method according to claim 2, further comprising:at the second
Wireless Sensor Network Gateway node, determining that the resource has
moved to the Wireless Sensor Network served by the second Wireless Sensor
Network Gateway node;determining whether a record of a subscription
request exists for the resource associated with the identifier; andin the
event that a record of a subscription request exists for the resource
associated with the identifier, informing the central resource tracking
function that the resource associated with the identifier has moved to
the Wireless Sensor Network served by the second Wireless Sensor Network
Gateway node.

4. The method according to claim 1, further comprising:at the first
Wireless Sensor Network Gateway node, determining that the resource has
moved out of the Wireless Sensor Network served by the first Wireless
Sensor Network Gateway node, and terminating the subscription with the
central resource tracking function.

5. The method according to claim 1, further comprising:at the central
resource tracking function, mapping and storing the identifier associated
with the tracked resource to an identity of the tracked resource received
from the location application node.

6. The method according to claim 5, further comprising:changing the
identifier associated with the tracked resource to a new identifier
associated with the tracked resource; andmapping and storing the new
identifier associated with the tracked resource to the identity of the
tracked resource.

7. The method according to claim 1, further comprising:at the central
resource tracking function, receiving a request from a location
application node to cancel resource tracking; andbroadcasting a
subscription cancellation message to the plurality of Wireless Sensor
Network Gateway nodes, the subscription cancellation message including
the identifier associated with the tracked resource.

8. A central resource tracking node for use in a communication network,
the node comprising:a first receiver configured to receive a request from
a location application node to track a resource;a processor configured to
generate a subscription message, the subscription message including an
identifier associated with the tracked resource;a transmitter configured
to transmit the subscription message to a plurality of Wireless Sensor
Network Gateway nodes; anda second receiver configured to receive from a
first Wireless Sensor Network Gateway node a subscription response
message informing the central resource tracking node that the resource
associated with the identifier is located in the Wireless Sensor Network
served by the first Wireless Sensor Network Gateway node, and to receive
from a second Wireless Sensor Network Gateway node a subscription
rejection message.

9. The central resource tracking node according to claim 8, further
comprising:a memory configured to store a mapping between the identifier
associated with the tracked resource and the identity of the tracked
resource received from the location application node.

10. A Wireless Sensor Network Gateway node comprising:a receiver
configured to receive from a central resource tracking node a
subscription request message, the message including an identifier
associated with a tracked resource;a processor configured to determine
whether the tracked resource is located in a Wireless Sensor Network
served by the Wireless Sensor Network Gateway node; anda transmitter
configured, in the event that the resource associated with the identifier
is located in the Wireless Sensor Network, to send to the central
resource tracking node a subscription response message, and in the event
that the resource associated with the identifier is not located in the
Wireless Sensor Network, to send to the central resource tracking node a
subscription rejection message.

11. The Wireless Sensor Network Gateway node according to claim 10,
further comprising:a memory configured to store a record of the
subscription request message.

12. The Wireless Sensor Network Gateway node according to claim 11,
further comprising:an input configured to determine that a new resource
has moved to the Wireless Sensor Network served by the Wireless Sensor
Network Gateway node, wherein the processor is configured to determine
whether a record of a subscription request exists for the new resource
and the transmitter is configured to, in the event that such a
determination is made, transmit to the central resource tracking node a
message informing the central resource tracking node that the resource
has moved to the Wireless Sensor Network served by the Wireless Sensor
Network Gateway node.

13. The Wireless Sensor Network Gateway node according to claim 10,
comprising:an input configured to determine that the resource has moved
out of the Wireless Sensor Network served by the Wireless Sensor Network
Gateway node, wherein the transmitter is configured to, in the event of
such a determination, transmit to the central resource tracking node a
message terminating the subscription with the central resource tracking
node.

Description:

TECHNICAL FIELD

[0001]The invention relates to the field of tracking network resources,
and in particular to the field of tracking network resources in a
Wireless Sensor Network.

BACKGROUND

[0002]Wireless Sensor Networks (WSNs) include a plurality of spatially
distributed sensor nodes that monitor physical conditions in a real world
environment, and are used in environment and habitat monitoring, traffic
control, home automation and stock tracking. Most current solutions that
utilize sensors are vertical in their implementation. The operator is
used as a bit pipe, and each WSN implementation uses its own protocols.
As in the case of classical networks, applications that use data
collected by sensor nodes in the WSN have their "channel" towards the
sensor nodes. Each application is tailor-made containing specialized and
in most instances proprietary components. Furthermore, there is no cross
utilisation of data and sensors between different services. This
situation leads to high development costs and relatively high costs for
implementations and operating. Typical examples of such applications are
industrial applications such as fleet management and logistics.

[0003]The integration of a WSN with a telecommunication network offers a
network environment convenient for new and appealing WSN based services,
for example smart home appliances, services for disabled and elderly
people and so on. Furthermore, such integration may allow more flexible
and efficient use of collected data. Data collected from sensor nodes
comprising a WSN can be made available to a communications network via a
WSN gateway.

[0004]Horizontal solutions offer a layered system design, based on the
reuse of common functions and services in a distributed (networked)
system. Different layers include clients (e.g., users, applications),
middleware control functions, and sensor networks. Such an approach
offers a clear separation between layers and hides WSN specifics from
clients. Middleware functions provide a mapping between client requests
and available WSNs.

[0005]Location based services (LBS) refer to a family of services that are
based on utilizing information regarding the location of resources.
Resources include anything that can be monitored, such as an object,
person or animal. Location acquiring can be network or device based. In
device-based positioning, using for example Global Positioning System
(GPS), all position calculation is performed locally at the device (or
resource). In order to use a location aware application, the locally
calculated position has to be transmitted to the application, to make the
application aware of the location of the resource.

[0006]LBSs in WSNs are mainly network-based. While device-based
positioning guarantees privacy and full control of the locally calculated
position disclosure, a problem with network-based positioning is that the
positioned resource (which may be, for example, an end user in a
communications network) is not in full control of its position data, thus
creating concerns regarding privacy. For WSN monitoring, tracking, and
resource controlling applications, strict security and privacy
requirements may be imposed by the owners of resource tracking tags.

[0007]With regards to resource tracking, when a tracked resource moves
from one WSN cover area to another, this may be referred to as roaming or
handover. Sensor data for the roaming tracked resource must be acquired
in a scalable way. An existing solution to track resources includes using
a Session Initiation Protocol (SIP) subscription event framework and
principles as defined by the IETF. In this case a central monitoring node
sends an initial subscription (SIP SUBSCRIBE) for location information to
each covered WSN. Each WSN accepts this subscription and is able to
seamlessly notify (using the SIP NOTIFY message) the central monitoring
node when a resource enters its cover area. A problem with this solution
is scalability. If m is the number of active tracked resources and n is
the number of WSNs, then this solution require m x n active subscription
sessions with the central monitoring node, as IETF standards require that
a SIP NOTIFY cannot be sent unless there is an active session.

[0008]An alternative solution, also based on the use of IETF standards, is
to improve the usage of the SIP publication framework. Each WSN sends a
SIP PUBLISH message to the central monitoring node with a list of
resources for which the WSN has location information. When handover is
detected, a WSN sends an updated PUBLISH message to the central
monitoring node. In this case, the central monitoring node would know
which WSN has the location information for a particular resource, and so
does not need to broadcast a subscription to all WSNs. A problem with
this approach is that there may be many resources whose location can be
determined by a WSN, but are not of interest to the central monitoring
node. With resources frequently moving from one WSN cover area to
another, there is redundant signalling traffic as each WSN publishes
changes to the central monitoring node even if there is no location aware
application that is interested in signalled resource location
information.

[0009]There are therefore issues with maintaining privacy and monitoring
roaming tracked resources in a way that optimized network traffic.

SUMMARY

[0010]According to a first aspect of the invention, there is provided a
method of tracking resources in a communication network. A central
resource tracking function receives a request to track a resource from a
location application node. The central resource tracking function
broadcasts a subscription message to a plurality of Wireless Sensor
Network Gateway nodes. The subscription message includes an identifier
associated with the tracked resource. The central resource tracking
function then receives a subscription response message from a first
Wireless Sensor Network Gateway node informing the central resource
tracking function that the resource associated with the identifier is
located in the Wireless Sensor Network served by the first Wireless
Sensor Network Gateway node, and receiving from a second Wireless Sensor
Network Gateway node a subscription rejection message. In this way, the
central resource tracking function becomes aware of the Wireless Sensor
Network in which the resource is located without requiring an active
subscription with all Wireless Sensor Network Gateway nodes and without
needing to receive signalling relating to nodes that the central resource
tracking function is not interested in.

[0011]As an option, the second Wireless Sensor Network Gateway node stores
a record of the subscription request. This allows the second WSN Gateway
node to be aware that the central resource tracking node is interested in
tracking the location of the resource, and this information can be used
if the resource moves into an area served by the second WSN Gateway node.
As a further option, if the second WSN Gateway node, determines that the
resource has moved to the WSN served by the second WSN Gateway node, then
a determination is made as to whether a record of a subscription request
exists for the resource associated with the identifier. If so then the
central resource tracking function is informed that the resource
associated with the identifier has moved to the WSN served by the second
WSN Gateway node.

[0012]Optionally, the method comprises determining at the first WSN
Gateway node that the resource has moved out of the WSN served by the
first WSN Gateway node, and terminating the subscription with the central
resource tracking function.

[0013]In order to maintain privacy of the tracked resource, the central
resource tracking function optionally maps and stores the identifier
associated with the tracked resource to an identity of the tracked
resource received from the location application node. To further increase
security and privacy, the method optionally comprises changing the
identifier associated with the tracked resource to a new identifier
associated with the tracked resource, and mapping and storing the new
identifier associated with the tracked resource to the identity of the
tracked resource.

[0014]As an option, the central resource tracking function receives a
request from a location application node to cancel resource tracking. On
receipt of this request, the central resource tracking function
broadcasts a subscription cancellation message to the plurality of WSN
Gateway nodes, the subscription cancellation message including the
identifier associated with the tracked resource. This informs all of the
WSN Gateway nodes that the central resource tracking function is no
longer interested in tracking the location of the resource.

[0015]According to a second aspect of the invention, there is provided a
central resource tracking node for use in a communication network. The
node is provided with a first receiver for receiving a request from a
location application node to track a resource, and a processor for
generating a subscription message. The subscription message includes an
identifier associated with the tracked resource. A transmitter is
provided for transmitting the subscription message to a plurality of WSN
Gateway nodes. Furthermore, a second receiver is provided for receiving
from a first WSN Gateway node a subscription response message informing
the central resource tracking node that the resource associated with the
identifier is located in the WSN served by the first WSN Gateway node,
and receiving from a second WSN Gateway node a subscription rejection
message.

[0016]Optionally, the node is provided with a memory for storing a mapping
between the identifier associated with the tracked resource and the
identity of the tracked resource received from the location application
node. This improves the privacy of the identity of the tracked resource.

[0017]According to a third aspect of the invention, there is provided a
Wireless Sensor Network Gateway node. The WSN Gateway node is provided
with a receiver for receiving from a central resource tracking node a
subscription request message. The message includes an identifier
associated with a tracked resource. The WSN Gateway node is also provided
with a processor for determining whether the tracked resource is located
in a WSN served by the WSN Gateway node. A transmitter is provided for,
in the event that the resource associated with the identifier is located
in the WSN, sending to the central resource tracking node a subscription
response message, and in the event that the resource associated with the
identifier is not located in the WSN, sending to the central resource
tracking node a subscription rejection message.

[0018]The WSN Gateway node is optionally provided with a memory for
storing a record of the subscription request message. In this case, the
WSN Gateway node is optionally also provided with an input for
determining that a new resource has moved to the Wireless Sensor Network
served by the Wireless Sensor Network Gateway node, wherein the processor
is arranged to determine whether a record of a subscription request
exists for the new resource and the transmitter is arranged to, in the
event that such a determination is made, transmit to the central resource
tracking node a message informing the central resource tracking node that
the resource has moved to the WSN served by the WSN Gateway node.

[0019]As an option, the WSN Gateway node is provided with an input for
determining that the resource has moved out of the WSN served by the WSN
Gateway node. In this case, the transmitter is arranged to transmit to
the central resource tracking node a message terminating the subscription
with the central resource tracking node.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 illustrates schematically in a block diagram a network
architecture according to an embodiment of the invention;

[0021]FIG. 2 is a signalling diagram showing signalling required to
maintain privacy of tracked resources according to an embodiment of the
invention;

[0022]FIG. 3 illustrates schematically in a block diagram registration of
Wireless Sensor Networks with a central resource monitoring function
according to an embodiment of the invention;

[0023]FIG. 4 illustrates schematically in a block diagram initiation of
resource tracking by a central resource monitoring function according to
an embodiment of the invention;

[0024]FIG. 5 illustrates schematically in a block diagram initiation of a
handover procedure when a resource moves from one Wireless Sensor Network
to another according to an embodiment of the invention;

[0025]FIG. 6 illustrates schematically in a block diagram initiation of a
cancellation procedure of resource tracking according to an embodiment of
the invention;

[0026]FIG. 7 is a flow diagram illustrating the steps of an embodiment of
the invention;

[0027]FIG. 8 illustrates schematically in a block diagram a node having a
resource monitoring function according to an embodiment of the invention;
and

[0028]FIG. 9 illustrates schematically a Wireless Network Gateway node
according to an embodiment of the invention.

DETAILED DESCRIPTION

[0029]Referring to FIG. 1, a Sensor Brokerage System (SBS) function 1 is
provided to act as a central resource monitoring node. Location aware
applications 2, 3 can access the SBS 1 to find information on a tracked
resource. The SBS 1 can communicate with various Wireless Sensor Networks
(WSNs). In this example, WSN1 4, WSN2 5 and WSNn 6 are shown, which
communicate with the SBS 1 via WSN gateways 7, 8 and 9 respectively. A
tracked resource 10 is also shown, currently residing in the area of WSN1
4. The tracked resource is provided with some way of identifying the
resource 10 to a WSN 1, such as a tracking tag. The tracking tag may be
as simple as a RFID tag, or can have a processor that generates a
presence tag ID. The tracked resource may be aware that it is to be
tracked, in which case it may be responsible for disclosing its WSN
identification to the SBS in a secure way. Alternatively, a resource that
is not aware of tracking is disclosed to the SBS by a third party
interested in tracking the resource. The term "resource" is used herein
to refer to anything that can be tracked, and can include an object such
as physical goods or a person, or may also include tracking of any sensor
readings that may move throughout a region covered by a WSN. An example
of this is, for example, tracking the movement of a chemical cloud across
a region covered by the WSN.

[0031]The SBS 1 is considered a trusted entity responsible for resolving
the identity of a resource tracking tag and returning necessary
information (e.g., positioning information) to the application 2. The
actual resource identity is thereby hidden from the WSN 4.

[0032]The tracking tag does not directly identify the tracked resource 10.
Instead, it may be an arbitrarily assigned code. The SBS 1 can obtain the
coded information and map it to an identity of the tracked resource 10.
In this way, a location aware application 1 can be made aware of the
location of the tracked resource 10, whilst the WSN 4 has no way of
identifying the tracked resource 10.

[0033]The basic concept is illustrated in FIG. 2. WSN1 4 and WSN2 5 make
the SBS 1 aware S1 of their services. The SBS binds S2 the tracking tag
ID with the tracked resource 10 to allow it to track the resource 10. A
Location Aware application 2 instructs S3 the SBS 1 to make it aware when
a resource having the tracking tag ID enters the area covered by WSN2 5.
In this example, WSN2 5 covers building A, and so the location aware
application is requesting notification when the tracked resource enters
building A. The SBS 1 sends messages S4, S5 to WSN1 4 and WSN2 5 to track
the tracked resource 10. The resource is initially located in WSN1 4.
WSN1 4 provides S6 the position of the tracked tag to the SBS 1. When the
tracked resource 10 leaves WNS1 4 and enters WSN2 5, WSN2 5 sends a
message S7 to the SBS 1 informing the SBS 1 of the position of the
tracked tag. The SBS 1 maps the tracked tag to the identity of the
tracked resource 10, and sends a message S8 to location aware application
2 to inform it that the resource has entered building A. In this way, the
privacy of the resource is maintained because the resource is not
identified between the WSNs 4, 5 and the SBS 1.

[0034]The disclosure of the resource/tracking tag ID pair can be done off
line or on line. Different mechanisms can be deployed in order to prevent
disclosure of the resource/tracking tag ID pair to a third party, such as
the generation of a new temporary random tracking tag ID for every
session. Another way of minimizing the possibility for external parties
to track the entity is to let the tracked device emit r, hash (r|| tag
ID) where r is a random number and hash is a one way function. This
effectively makes it impossible to track the device without knowledge of
the tag ID.

[0035]To summarize, the SBS 1 creates and maintains a record with the
resource/tracking tag ID pair. The location aware application 2 queries
the SBS 1 for the position of the resource using a signalling protocol
such as SIP. The SBS 1 substitutes the resource identity with its valid
tracking tag ID and queries all sensor networks, i.e., WSN gateways that
provide location services for the tracking tag type of technology using a
signalling protocol such as SIP. The SBS 1 uses event notification
mechanisms to subscribe to WSN gateways to receive updates of the
tracking tag location.

[0036]WSN gateways publish their location services to the SBS 1.
Publishing may include area of coverage and location metrics as well as
global references such as geographical coordinates in order to place the
WSN area of coverage into a global location context. Publishing can be
off line or on line.

[0037]Another aspect of the SBS 1 is the support for seamless roaming of
the tracked resource 10 between WSNs. When a resource tracking request is
received by the SBS 1, the SBS broadcasts location subscriptions to find
out which WSN has the required resource location information. In this
way, the SBS also implicitly informs other WSNs which do not currently
have the required information to track the particular resource in the
case of handover. The location subscription is accepted only by the WSN
that currently knows the resource location. Other WSNs formally reject
the subscription, but keep a list of resources whose locations have been
requested by the SBS 1. The list is referred to as a resource record
list. This allows for so-called "one sided statefullness", since the SBS
1 receives subscription rejections and does not have to monitor the state
of each sent subscription. When handover occurs, the resource record list
maintained by a WSN will allow the WSN to inform the SBS 1 about location
awareness for the resource whose location information has been previously
requested. The following description provides an example of this, and
assumes that communication between the SBS 1 and WSNs is based on the SIP
protocol, although it will be appreciated that other communication
protocols may be used.

[0038]Referring now to FIG. 3, each WSN GW 7, 8, 9 registers each WSN 4,
5, 6 with the SBS 1 by sending a SIP REGISTER request S9, S10, S11
respectively. In this example, the tracked resource 10 in question is
located in the area covered by WSN 1 4.

[0039]Referring now to FIG. 4, when a location aware application 2
initiates a resource tracking request S12, the SBS 1 starts procedures to
find out which WSN knows the requested resource location information. A
location subscription (SIP SUBSCRIBE) S13 is sent by the SBS 1 to each
WSN 4, 5, 6, the message including information identifying the tracked ID
tag. A location filter event definition may be included in the message
body to indicate to each WSN 4, 5, 6 the conditions under which the WSN
should send a notification (e.g., when a resource enters a particular
area).

[0040]In this example, the WSN GW 7 of WSN1 4 knows that the resource
having the tracked ID tag is in its area, and so respond(s) with a 200 OK
message S14. Other WSNs 5, 6 that do not know the resource location
respond with a 404 Not Found message (not shown).

[0041]The WSN 4 that accepts the subscription responds with SIP NOTIFY
requests S15 carrying location information, while other WSNs 5, 6 keep a
record of the tracked ID tags in a resource record list. The SIP NOTIFY
contains a Presence Information Data Format Location Object (PIDF-LO),
enabling the encapsulation of location information within a presence
document (according to IETF RFC 4119).

[0042]Considering now the case where the tracked resource moves from WSN1
4 to WSN2 5, and referring to FIG. 5, if WSN1 4 can no longer determine
the location of the tracked ID tag, it terminates the subscription by
sending a terminating SIP NOTIFY request S16 to the SBS 1. However, WSN1
4 keeps a record of the tracked ID tag in the case the resource moves
back to the WSN1 4 coverage area.

[0043]WSN2 5 detects that a resource (having a tracked ID tag from a
resource record list) has entered its coverage area, and so because it
knows from the record of tracked ID tags that the resource having this ID
is being tracked by the SBS 1, sends a SIP PUBLISH method S17 to the SBS
1 to inform the SBS 1 that WSN2 5 is the new designated WSN for the
resource having the tracked ID tag. After the SBS 1 receives this SIP
PUBLISH method, it creates and sends a new subscription (SIP SUBSCRIBE
request) S18 to WSN 2 5. WSN2 5 responds with SIP NOTIFY requests S19
carrying new tracked ID tag location information.

[0044]Procedures for resource tracking cancellation are shown in FIG. 6.
When resource tracking is no longer needed, a location aware application
2 sends a resource tracking cancellation request S20 to the SBS 1. The
SBS then initiates subscription cancellation by sending SIP SUBSCRIBE
messages S21 with the "Expires" header set to zero to each WSN 4, 5, 6.
The designated WSN (in this example, WSN2 5, as this is the WSN where the
tracked resource is currently located) removes and terminates the
location subscription, while other WSNs 4, 6 must remove the tracked tag
ID from the resource record list.

[0045]Referring now to FIG. 7, the flow diagram illustrates how the
tracking tag and the subscriptions work together to improve privacy and
reduce signalling. The following numbers refer to the numbering of FIG. 7
and the previous figures, in order to maintain consistency:

[0046]S12. The SBS 1 receives a request from a location aware application
2 to track a resource 10.

[0047]S2. The SBS 1 binds an identity of the resource with a tracking tag
ID and stores the binding. The tracking tag ID can only be used by the
SBS to identify the resource 10.

[0048]S9. The SBS broadcasts a subscription to a plurality of WSNs 4, 5,
6, the subscription including the tracked tag ID.

[0049]S14. A WSN GW 7 that serves the WSN 4 in which the resource having
the tracked tag ID is located sends a subscription response message to
the SBS 1, and all other

[0051]S23. The WSN GWs 8,9 that sent a rejection message maintain a record
of the subscription request, so that they are aware that a subscription
is outstanding to track a resource associated with the matching tracked
tag ID.

[0052]S24. The tracked resource 10 moves to an area covered by a new WSN
5.

[0053]S25. The WSN GW 8, or another node in the new WSN, determines
whether a prior subscription request has been recorded for the resource
associated with the tracked tag ID.

[0054]S17. If so, then the new WSN GW 8 informs the SBS 1 of the location
of the tracked resource 10 using a SIP PUBLISH method.

[0055]S16. As the tracked resource has moved out of the area covered by
the old WSN 4, the old WSN GW 7 terminates its subscription with the
SBS1. Note that this step can occur before the new WSN GW 8 sends a SIP
PUBLISH method to the SBS 1, and the receipt of such a subscription
termination message at the SBS 1 can trigger the SBS 1 to broadcast a new
SIP subscription request in order to find the location of the tracked
resource 10.

[0056]Whilst the above description with respect to FIGS. 3 to 7 refers to
the WSNs keeping a record of the tracked tag ID, it will be appreciated
that where privacy is not an issue, the same system can be used to keep
track of information that may be used to directly identify the tracked
resource, such as a MAC address or a SIP address.

[0057]Referring now to FIG. 8, there is illustrated a SBS function node
according to an embodiment of the invention. The SBS 1 function node
comprises a first receiver 10 for receiving messages from location aware
applications 2, and a second receiver 13 for receiving messages from WSN
gateways 7, 8, 9. Of course, the two receivers may be embodied in the
same physical device. A processor 11 is provided for processing and
generating messages, and a transmitter 12 is also provided for sending
messages to location aware applications 2, 3 and WSN gateways 7, 8, 9.
The SBS 1 further comprises a memory 13 for storing information relating
to tracked resources and tracked tag IDs.

[0058]Referring now to FIG. 9, there is illustrated a WSN GW 7 according
to an embodiment of the invention. The WSN GW 4 comprises an input 19 for
receiving information relating to a tracked resource 10 located in an
area covered by the WSN 4. A processor 15 is provided for processing and
generating messages. Furthermore, a transmitter 17 and a receiver 15 are
provided for sending messages to and receiving messages from a SBS 1. A
memory 18 is provided for storing information relating to tracked
resources in the area covered by the WSN 4, and for maintaining a record
of resources tag IDs for which the WSN GW 7 has received a subscription
request, as described above. A processor 16 is also provided for
generating messages.

[0059]The invention reduces the signalling required when a tracked
resource moves between WSNs, and improves the privacy of information that
may be used to identify a tracked resource. WSNs and their positioning
capabilities are integrated with telecommunications networks supporting
full control of privacy disclosure.

[0060]It will be appreciated by the person of skill in the art that
various modifications may be made to the above-described embodiments
without departing from the scope of the present invention. For example,
whilst the above description refers to acquiring the location of
resources in a wireless network, the resources referred to may be any
object, such as goods, a person, and so on. The term "resources" refers
to anything that moves in a WSN that can be tracked. An example of this
is, for example, tracking a chemical cloud as it moves through an area.